1. Field of the Invention
The present invention relates to a regenerative braking system for a hybrid vehicle using an active booster master cylinder.
2. Disclosure Information
Hybrid vehicles, such as hybrid electric vehicles, use complex brake systems requiring independent wheel brake control. Some vehicles utilize hydraulic brake-by-wire systems including a high pressure accumulator, a pedal feel emulator, advanced analog valves, a pump, and motor. Typically, current master cylinder units are quite large because of the need to package an active booster as well as a pedal feel emulator together. As used herein, the term “pedal feel emulator” refers to a device which simulates the force/displacement characteristics of a conventional master cylinder and booster assembly, in response to input from a motorist. Emulators are used to produce so-called “transparency” in braking response, whether the vehicle is being braked regeneratively or with a combination of regenerative and friction braking, or solely with the use of friction braking. Also, as used herein, the term “active booster” refers to a device which provides not only an amplification or boosting of force between a mechanical input and a mechanical output, but also an electronically commanded boosted output independent of the mechanical input. Known active boosters utilize stored vacuum as an energy source, but other types of electronic or hydraulic boosters are known to those skilled in the art.
It would be desirable to provide a braking system for a hybrid vehicle in which an active booster master cylinder may be mounted remotely from a primary master cylinder which is actuated by the motorist.